Paper-making-machine fabric and tissue paper produced therewith

ABSTRACT

The invention relates to a paper machine clothing, notably an air-dry clothing (TAD clothing), in the form of a woven having a weaving design. According to the invention the relative depth of machine clothing cups which are open towards the contact surface of the paper is 20% or more, said relative cup depth being the quotient of the difference between the measurement height for which the bearing percentage is 30% and the measurement for which the bearing percentage is 60% on the one hand, and the sum of the diameters of a warp thread and a weft, on the other hand. The measurement height “0” is the outer limit of the paper machine clothing on the paper contact surface, the bearing percentage is the projected sectional area of the threads of the woven at a given measurement height in relation to the measurement surface, the section areas being parallel to the surface of the clothing. The invention also relates to a tissue paper product which is produced with such a clothing and is especially voluminous in direction Z.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The technical field of the invention relates to the production oftissue paper on a corresponding paper-making machine in which moreparticularly a through air drying (TAD) zone is provided. In this TADzone a special imprinting fabric is employed.

[0003] 2. Prior Art

[0004] The sheet formation of the paper and the three-dimensionalstructuring of an already formed moist fiber felt which is stilldeformable, however, due to a remaining high water content, is usuallydone on backing woven fabrics stemming from textile weave processes.

[0005] Three-dimensionally structuring a moist paper web by formingzones of low density framed by dense zones is undertaken in modem tissuemaking machines in the course of predrying the sheet in a predryingsection upstream of the yankee cylinder. Predrying the paper web occurson the backing fabric by convection in forcing hot air through the paperweb located on the backing fabric. This is termed through air drying(TAD).

[0006] Three-dimensional structuring is usually implemented in threesteps mostly sited separately in sequence. The first step involvesdeflecting the fibers in the Z direction into the structuringdepressions in the backing fabric made available by the TAD imprintingfabric systematically distributed over the surface area of the backingfabric contacting the paper. Deflecting the fibers in the Z direction isprompted by a flow of air and water, vacuum-assisted by one or morevacuum boxes arranged on the side of the backing fabric opposite theside in contact with the paper.

[0007] Deflecting the fibers in the Z direction into the interior of thedepressions results in zones of reduced density in the paper sheet whichare termed pillows. These zones of reduced density arranged in a patternare dried in a second step on or in the interior of the backing fabricby the air flowing therethrough of one or more TAD cylinders and thusset in the existing distribution of the fibers, i.e. “freezing” thefiber distribution status.

[0008] Then, in a third step partial compression of the predried fiberfelt takes place by pressing the backing fabric with the predried web ofpaper located thereon with the aid of a compression roller against thesurface of the yankee cylinder. Compression of the paper web occurs inthe raised portions of the backing fabric which may be formed by bothwarp and weft wires in the predefined portions of the backing fabricsurface. The fibers located in the depressions of the backing fabricreceive no compression. TAD imprinting fabrics as the backing fabricrepresent a special type of fabric comprising typical structurizingproperties by their weave, choice of wire as regards material, diameter,cross-sectional shape and after-treatment, for example, heat setting andgrinding of the surface.

[0009] Paper-making-machine fabrics are known for example from WO96/04418, DE-OS 30 08 344, EP 0 724 038 A1.

SUMMARY OF THE INVENTION

[0010] The technical problem (object) of the invention involvesproviding a paper-making-machine fabric which is suitable andconfigured, as regards a tissue paper having an enhancedthree-dimensional surface structure in the form of a sequence of pillowsand pockets, to achieve a tissue paper of enhanced visual appeal,improved softness and greater volume in conjunction with an improvedwater absorption and better feel.

[0011] This problem is solved more particularly by the features of claim1.

[0012] Due to the solution in accordance with the invention apaper-making-machine fabric is provided in which exceptionally deeppockets are provided with the result that more particularly in the TADzone with this paper-making-machine fabric a paper and, moreparticularly, a tissue paper is producible which features anexceptionally large three-dimensional structure as regards an increasein the specific volume which makes the paper appear particularly fluffyand features in addition to exceptional softness also exceptionally goodwater absorption. In addition to this, an enhanced similarity to a wovenstructure and thus to the look and feel of cloth is achieved.

[0013] With the paper-making-machine fabric as described, a paperstructure is producible having a large number of pillow-like zones ofreduced density provided systematically distributed over the fullsurface area of the fiber felt. The extent of the pillow-like zones ofreduced density in the Z direction, i.e. their thickness, is a maximumrelative to their size in surface. Each low-density pillow-like zone isevidently separated from its adjacent pillow-like zone by a line-typeframe of increased density, this line-type frame being formedcontinuously or discontinuously by interruptions. The line portionsvisually appearing continuous are characterized by a greatly increased,even density as compared to the low-density of the pillow-like zones. Ifthe line portions are interrupted, the line portions in the region ofthis interruption feature a low density as compared to that of thecontinuously appearing line portions which, however is significantlyhigher as compared to that of the pillow-like zones.

[0014] The line-type frames dictate the surface-area extent of thepillow-like zones. The entirety of the pillow-like zones with theirline-type frames furnishes a visually obvious macroscopic distributionpattern which is typical for TAD imprinting fabric used for structuringand its weave and finish.

[0015] In this arrangement the three-dimensional structure produced inthe fiber felt with its typical pattern is the mirror image of thethree-dimensional structure and distribution pattern of the fabric usedin production. More particularly when employing TAD and moreparticularly when increasing the density as mentioned above isundertaken at the drying cylinder the tissue papers produced inaccordance with the invention feature, as compared to non-structuredtissue papers produced conventionally, a significantly increasedspecific volume with added fluffiness as well as an enhanced absorptioncapacity for liquids, especially water.

[0016] Also as compared to conventional TAD paper-making-machine fabricsthe TAD paper-making-machine fabrics in accordance with the inventionproduce a paper having a significantly increased specific volume, addedfluffiness and improved liquid absorption capacity.

[0017] Further aspects read from the sub-claims. A further increase inthe depth of the pockets is achievable by the features of claim 2. Fromthe remaining sub-claims a series of example embodiments materializes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Illustrated in the drawings are example embodiments of theinvention in which:

[0019]FIG. 1 is a schematic three-dimensional drawing illustrating thedefinition of the bearing-area-percentage;

[0020]FIG. 2 is an illustration showing the sensor of the measuringmeans and the measuring direction;

[0021]FIG. 3 is an illustration showing a fabric specimen under thetriangulation sensor;

[0022]FIG. 4 is a rough drawing illustrating the actual cross-section ofa TAD fabric with support material;

[0023]FIG. 5 is a rough drawing illustrating the measuring result;

[0024]FIG. 6 is a rough drawing illustrating the selected scaled contactplane;

[0025]FIG. 7 is a cross-sectional illustration defining relativearea-percentage and the bearing-area-percentage as shown in FIG. 1;

[0026]FIG. 8 is a graph plotting the relative area-percentages for SCA 1fabric;

[0027]FIG. 9 is a graph plotting the bearing-area-percentage for SCA 1fabric;

[0028]FIG. 10 is an illustration of 30% and 60% bearing-area-percentage;

[0029]FIG. 11 is an illustration of the idealized fabric thickness;

[0030]FIG. 12 is an illustration of a BST-type comparison fabric asviewed from the paper side;

[0031]FIG. 13 is an illustration of a 44 GST type comparison fabric asviewed from the paper side;

[0032]FIG. 14 is an illustration of a 44-MST-type comparison fabric asviewed from the paper side;

[0033]FIG. 15 is an illustration of a SCA-1-type fabric in accordancewith the invention as viewed from the paper side;

[0034]FIG. 16 is an illustration of a SCA-2-type fabric in accordancewith the invention as viewed from the paper side;

[0035]FIG. 17 is an illustration of a SCA-3-type fabric in accordancewith the invention as viewed from the paper side;

[0036]FIG. 18 is an illustration of a SCA-4-type fabric in accordancewith the invention as viewed from the paper side;

[0037]FIG. 19 is an illustration of a SCA-5-type fabric in accordancewith the invention as viewed from the paper side.

DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0038] The system for measuring the fabric will now be explained by wayof a SCA-1-type fabric in accordance with the invention. The term“screen” will be used thereby synonymously for fabric.

[0039] I. UBM Measuring System:

[0040] Triangulation sensor OTM2 of the Company Wolf & Beck

[0041] Controller: base unit RS 232 incl. sync socket

[0042] Table: (DC(Galil) motor controlled measuring table with 2 axes;

[0043] Travel: 50 mm; lateral resolution per axis <1 82 m

[0044] This system is furnished complete by the Company UBM MesstechnikGmbH (Ottostr. 2, D-76275 Ettlingen). TABLE 1 General operating data,accuracy and laser data of the triangulation sensor OTM2 Generaloperating data Accuracy Work spacing Brightness dynamics (single sensorsetting (front lens <−> measuring range middle) 45 ± 1 mm sufficient foroperation from bright aluminium surface to black rubber material) 25 dBMeasuring range 10 ± 1 mm Measuring capability dull black referencesurface to a sampling angle of 45° Resolution 1 μm Reproducibility forinclination <5° on reference standard <0.005 mm for inclinations >5° to60° <0.01 mm Surface suitable for measuring Diffuse Maximum linearityerror Partly reflecting for inclination <5° on reference standard <0.02mm for inclinations >5° to 60° <0.05 mm Temperature range +10-+40° C.Maximum stray light influence <0.005 mm (change in ambient brightnessfrom radiation intensity 0 to 100 W/m2) Relative humidity 80% Maximumtemperature drift (10-40° C.) <0.02 mm Laser data Influence of surfaceinclination  0.05 mm profile section over a reference ball angular range± 60°) maximum deviation Laser wavelength 750 nm Influence of surfacecolor  0 mm measured from 10 color reference samples over full measuringrange Minimum lase power (pulsed) <0.4 mW Maximum measuring deviation<0.03

[0045] The triangulation sensor OTM2 is an optoelectronic laser sensorfor non-contact distance measuring and comprising a sensor head andcontroller.

[0046] The sensor head is designed as a coaxial arrangement ofemitter/detector optics. The emitter optics comprise a visiblesemi-conductor laser including collimator optics. The laser beam has alow aperture and emerges centrally from the sensor head. The lightreflected diffusely from the surface is analyzed rotationallysymmetrical (360°) and contributes primarily to the gain in result. Amechanical structure having no moving parts permits high acceleration ofthe sensor head also during measuring.

[0047] To avoid stray light interference the intensity of the laser beamis modulated at a high frequency. The emitted beam power is regulated asa function of the measuring conditions. Thus reliable measuring ofsurfaces greatly differing in reflectivity is ensured. The detectedsignals are conditioned and digitized in the sensor head to thus ensurehigh immunity of the communication between sensor head and controller tointerference.

[0048] The controller contains a digital circuit for linearizing andtime-filtering the measured data. The results being output via thisinterface.

[0049] Table 1 provides an overview of the general operating data,measuring accuracy and laser data.

[0050] The measured data are stored in a data file and are available forprocessing by the UB Soft 1.9 software. Exporting the data in Excel isnot possible, however.

[0051] II. OPTIMAS 6.0 Software (Image Analysis)

[0052] This software is available from the Company Stemmer Imaging GmbH(Guten-bergstr. 11, D-82178 Puchheim).

[0053] III. Definition of Bearing-area-percentage

[0054] The bearing-area-percentage in the sense of the inventiondescribes the respective percentage of the sectional area through thematerial relative to the total area. The bearing-area-percentage is thendefined by the percentage of the area c×d relative to the total area a×b(FIG. 1). Fabrics having a very coarse structure feature only a slightincrease in the bearing-area-percentage when the change therein isrelated to the change in height.

[0055] IV. Specimen Preparation

[0056] 1. A 50×50 mm large piece is parted from the fabric SCA 1 bymeans of a soldering iron so that the edge of the fabric does not frayand the specimen remains dimensionally stable. However, the size of thespecimen is generally freely selectable. Selecting the area to be sensedand measured within the size of the specimen depends on the weavepattern of the fabric so that any edge interference distorting theresults is practically eliminated. For an 8 shed fabric having threaddiameters of 400×450 μm the area to be measured must thus be greaterthan 7×7 mm.

[0057] 2. The rear side (in contact with the glass plate serving as thesupport material) of the fabric is rubbed with emery cloth so that thecontact surface area is uniform and protruding pieces of thread releaseddue to parting of the specimen are removed.

[0058] 3. Clean fabric specimen with compressed air.

[0059] 4. Bond fabric specimen by double-sided sticky tape to a glassplate corresponding in size to that of the fabric specimen (50×50 mm).By it being fixed to the glass plate the fabric is prevented fromcorrugating and a flat surface is assured, i.e. the fabric remainsdimensionally stable.

[0060] 5. Spray fabric specimen with Blow-Flag (a removable masking ink,US production) to ensure uniform reflection as needed for the lasersensor. Metering the corresponding amount of masking ink is necessarysince spraying too much may clog the cavities in the fabric whilst toolittle diminishes the reflection.

[0061] 6. The specimen as prepared according to items 1 to 5 is thenplaced on the measuring table, taking into account the machine runningdirection of the fabric (see FIG. 2), so that the machine runningdirection of the fabric coincides with one axis (y-coordinate direction)of the 2-axes measuring table. Installed above the measuring table isthe triangulation sensor (FIG. 2). Aligning the specimen in the machinerunning direction is done by eye and is thus not always exact. FIG. 3shows the specimen under the triangulation sensor indicating themeasuring range, working spacing and detection range.

[0062] V. UBSoft Software Settings (see FIG. 2)

[0063] 1. Measuring distance: 12 mm, point density: 50 points/mm inmachine running direction and transversely thereto, i.e. 600×600 pointsare detected per measurement. The size of the measuring area to beselected is dictated by the repeat of the pattern. Thus, e.g. for an8-shed fabric a surface area greater than 8×8 threads is measured.

[0064] 2. Measuring is done incrementally by automatic advancement ofthe measuring table with the specimen affixed thereto along the twoadvancement axes at a “scanning rate” which is independent of themeasuring frequency. The scanning rate is 3 mm/s.

[0065] The travel of the specimen is indicated schematically on theright in FIG. 2. The starting point for measuring is the center-point(1), i.e. measuring starts at the center of the surface area. This isfollowed by an idle travel to the lower left-hand point of the surfacearea where actual measuring commences. On completion of measuring afterapprox 11 h in the top right-hand corner, an idle travel is instrumentedto the starting point. The measuring direction in this procedure is“forwards”, i.e. measuring is instrumented in forwards movement of thetable in the traverse and machine running direction.

[0066] 3. Only the results of measuring the profile are recorded.

[0067] VI. Analysis Using UBSoft Software

[0068] 1. Since, despite utmost care, it is impossible to locate thespecimen planoparallel under the sensor, the measured surface area needsto be initially aligned with the aid of mathematical methods on thebasis of the measured results to ensure that it appears planoparallel.For this purpose two different tools (linear regression and contactsurface area) are available.

[0069] The “linear regression” tool aligns a measuring sequence on thebasis of a regression plane. The plane is generated by the least squaresmethod from the points measured and plotted in the measuring graphicsand then subtracted from the measured data file.

[0070] The “contact plane” tool aligns the measured area according tothe three highest points.

[0071] For the SCA-1 fabric a height of 2638 μm is measured (maximum1006 μm, min −1632 μm). The measured area is aligned by the “contactplane” tool, resulting in a height of 2628 μm (maximum: 0 μm, min: −2628μm).

[0072] 2. Due to the open area or “holes” in TAD fabrics the graphicalrepresentation of the measuring result is not the same as the actualfabric (FIG. 4). As evident from FIG. 5 the optically closed areapercentages of the fabric appear deeper or thicker than the spacing ofthe surface of the support material to the laser sensor as measured,whereby the surface of the support material serves as the referenceplane. This results from the difference in the reflection factors offabric and support material. The actual thickness of the fabric SCA 1 asmeasured by a thickness tester (as per EN 12625-3: 1999) is 1778 μm.

[0073] 3. Since pre-treating the fabric with Blow-Flag has ensured auniform reflectivity of all wires of the fabric (screen) and only thedifferences in height between the surface of the warp and weft wiresforming the fabric are of interest, mal-measuring the absolute spacingto the surface of the support material (reference plane) is irrelevantfor all practical purposes and can thus be eliminated by scaling.

[0074] 4. Since the fabric “measuring height” (2628 μm) is substantiallygreater than the actual fabric thickness (1778 μm), the heights arefirstly defined or scaled to 1900 μm (max: 0 μm, min: −1900 μm), thisdefinition in the height being selected as a function of the actualfabric thickness. Should this amount to more than 1900 μm, all fabricsmust be defined to a higher degree (FIG. 6). This is why comparing theestablished results must only be done on specimens defined to the samedegree.

[0075] 5. Due to its internal analysis software and due to havingsuitably selected the measuring point spacing, the measuring system isable to “see” structurally associated values equi-spaced from the sensor(height, thickness). Structurally associated in this measuring proceduremeans that the measuring points to be analyzed are associated in eachcase to an explicitly defined surface, e.g. that of a single warp orweft wire.

[0076] Combining structurally associated points equi-spaced from thesensor (i.e. having the same height/thickness) produces the heights orcontour lines forming the definition of the section plane to the fabricmaterial, i.e. the warp and weft wires sectioned by the section plane ina specific height. It is from the spacing of contour lines ofstructurally associated elements of the fabric that the section areasassigned to a specific height and termed “bearing-area-percentage” canbe computed. It is to be noted that as of the largest expansion of thewarp or weft wires only the projected area and not the actual area istaken into account.

[0077] 6. Exporting the bearing-area-percentage curves from the UBSoftdata file into another program is not possible with the existingfacilities. This is why the aligned, defined areas are thus convertedinto the image data files (8-bit gray display, TIF format) forsubsequent further processing by the OPTIMAS image analysis software.

[0078] VII. OPTIMAS 6.0 Analysis

[0079] 1. Making the conversion into an 8-bit TIF data file means thatthe 1900 μm difference in height is converted into 256 brightness levels(0 to 255), i.e. maximum: brightness level 255=0 μm; min: brightnesslevel 0=−1900 μm). Using the PercentArea tool (rel. area percentage) therelative area-percentage of each of the 256 brightness levels isdetermined. This means that unlike the bearing-area-percentage not thestructural elements of the fabric assigned to a section plane areestablished but the structural elements associated with a brightnesslevel. Illustrated by way of example in FIG. 7 is a portion of the FIG.1 as a two-dimensional drawing to show the difference between relativearea-percentage and bearing-area-percentage. In this arrangement a1 toa5 are the structural elements of a brightness of 97 or height of −1177μm. These structural elements of the relative area-percentage take intoaccount only the brightness for a specific height or only the parts ofthe area appearing new since the previous section (for brightness 98 orheight −1170 μm). The relative area-percentage for the correspondingheights is formed by summing the individual structural elements a_(i),i.e.${{{relative}\quad {area}} - {{percentage}\quad {for}\quad {brightness}\quad 97}} = {\sum\limits_{i = 1}^{n}\quad a_{i}}$

[0080] In FIG. 7 b1 to b3 represent the structural elements of thebearing-area-percentage for a brightness of 97 or height of −1177 μm.The bearing-area-percentage of this height or brightness is formed bysumming the individual structural elements b_(i), i.e.:${{bearing} - {area} - {{percentage}\quad {for}\quad {height}} - {1177\quad \mu \quad m}} = {\sum\limits_{i = 1}^{n}\quad b_{i}}$

[0081] By summing the relative area-percentages up to a specificbrightness the bearing-area-percentage for this brightness or height canthus be computed, i.e.:${{bearing} - {area} - {\% \quad {for}\quad {brightness}\quad k}} = {{\sum\limits_{j = k}^{255}\quad {{relative}\quad {area}}} - {\% \quad {for}\quad {brightness}\quad j}}$

[0082] By summing the relative area-percentages from height 0 μm orbrightness 255 to height −1177 μm or brightness 97 thebearing-area-percentage is likewise formed, i.e.:${{bearing} - {area} - {\% \quad {for}\quad {height}} - {1177\quad \mu \quad m}}\quad = {{\sum\limits_{j = 97}^{255}\quad {{relative}\quad {area}}} - {\% \quad {for}\quad {brightness}\quad j}}$

[0083] To obtain the maximum bearing-area-percentage of 100% at theheight −1900 μm or brightness 0 all relative area-percentages from 0 to255 must be added. This is tabulated on the last page as an example forthe fabric SCA 1.

[0084] 2. The resulting data are then exported to Excel.

[0085] 3. FIG. 8 plots the relative area-percentages as a function ofthe thickness as computable from the brightness levels for the fabricSCA 1.

[0086] 4. Summing the individual “relative area-percentages” equi-spacedfrom the sensor (same height or thickness) then computes thebearing-area-percentage. The difference in height is then plotted as afunction of the bearing-area-percentage so that the change in heightbetween various bearing-area-percentages can be read off (FIG. 9).

[0087] Since the measured fabric SCA 1 was not ground, heights orthicknesses can also be read off for a bearing-area-percentage of lessthan 30%. For use in the tissue machine the fabric was, however, groundto a contact surface area of 30%, resulting in the profile of the curvemaking no difference as of a bearing-area-percentage of 30%.

[0088] 5. To assess TAD fabrics one of the limit values of thebearing-area-percentage should be 30%. A bearing-area-percentage of 30%needs to be selected because TAD fabrics are usually ground. Expertopinion is that TAD fabrics must not be ground in excess of 30% contactsurface area, corresponding to 30% bearing-area-percentage (FIG. 10).Although grinding effects the profile of the bearing-area-percentagebetween 0 and 30%, it has no effect above 30%, assuming not more than30% contact surface area is ground. This means that for a certainfabric—irrespective of grinding—the bearing-area-percentage of a groundand non-ground TAD fabric above 30% should be precisely the same.

[0089] In comparing several, different single-ply fabrics, this meansthat the relative area-percentages and bearing-area-percentages in FIG.2 are all scaled to 30% bearing-area-percentage of a fabric, i.e. thevalues of all other fabrics are shifted in the Table to a fabricbearing-area-percentage of 30%.

[0090] TAD fabrics have nearly always an open area or holes. This is whya bearing-area-percentage of 100% is not achieved in the fabric, atleast in theory. Although 100% bearing-area-percentage is indicated inmeasuring, this is only achieved by incorporating the support materiallocated under the fabric. To cancel out the effects of differing fabricthicknesses and structure of the support material employed whencomparing different single-ply fabrics, the range of thebearing-area-percentage needs to be defined upwards (cf. FIGS. 5, 6defining the result of measuring). The open area of the fabrics amountsto approx. 20 to 30% in most cases. When the bearing-area-percentage isdefined to 60%, the result is sufficiently remote from commencement ofthe result being influenced by the open area (FIG. 10).

[0091] When considering only the difference in height between 30% and60% bearing-area-percentage, the flat fabrics exhibit only a slightdifference in height, whereas heavily structured fabrics exhibit a muchgreater difference in height especially in this range. Table 2 lists theresults for analysing several TAD fabrics as in prior art, on the onehand, and as embodiments in accordance with the invention, on the other,and thus confirm this assumption. Structured fabrics exhibit adifference in height of more than 170 μm.

[0092] VIII. Relative Pocket Depth Percentage:

[0093] Due to the above definition the bearing-area-percentage isinfluenced very strongly by the warp and weft wire diameter employed,i.e. the thicker the wires the greater is the difference in heightbetween 30 and 60% bearing-area-percentage. To eliminate this influenceby the wire diameter it is good practice to relate the difference inheight between 30 and 60% bearing-area-percentage to the sum of thelargest warp and weft wire diameters and to term this classificationcharacteristic the “relative pocket depth”. The relative pocket depth isstated as a percentage. The relative pocket depth shows that highlystructured fabrics exhibit high values, the borderline betweenconventional and new fabrics being the value of 20%. Estimated values,i.e. in accordance with the difference in height relativised in FIG. 11are tabulated in Table. 2. TABLE 2 RESULTS OF SINGLE-PLY FABRICS BST 44GST 44 MST SCA 1 SCA 2 SCA 3 SCA 4 SCA 5 Height at 30% 1080 μm 1080 μm1080 μm 1080 μm 1080 μm 1080 μm 1080 μm 1080 μm Bearing-Area-% Height at60% 1147 μm  976 μm  991 μm  775 μm  872 μm  872 μm  827 μm  909 μmbearing-area-% Difference (30%-  126 μm  104 μm  104 μm  305 μm  208 μm 208 μm  253 μm  171 μm 60%) Diameter of warp  800 μm  850 μm  800 μm 850 μm  750 μm  750 μm  800 μm  800 μm and weft threads (400 × 400)(350 + 500) (400 × 400) (400 + 450) (350 × 400) (350 × 400) 350 × 450)(350 × 450) summed Bearing-Area-per-  15.8%  12.2%  11.1%  31.7%  27.7% 27.7%  31.6%  21.4% centage (30-60°) related to threads, i.e. relativepocket depth

[0094] Tabulated in the Table on the next page are the relativearea-percentages associated with the various heights computed from thebrightness levels (as established by the PercentArea tool in the Optimasprogram) and the bearing-area-percentages computed therefrom for the SCA1 fabric. It was with these numerical values that the plots as shown inFIGS. 8 and 9 were produced. A B C D E F G H I J K L M N O Bright- Rel.Area Bright- Rel. Area Bright- Rel. Area ness Height Area Bearing nessHeight Area Bearing ness Height Area Bearing 1 level [μm] % [%] % [%]level [μm] % [%] % [%] level [μm] % [%] % [%] 2 0 −1900 9.943 100.000 64−1423 0.081 85.351 128 −946 0.654 62.134 3 1 −1893 0.113 90.057 65 −14160.100 85.270 129 −939 0.681 61.480 4 2 −1885 0.103 89.944 66 −1408 0.09785.170 130 −931 0.674 60.799 5 3 −1878 0.105 89.841 67 −1401 0.09785.073 131 −924 0.689 60.125 6 4 −1870 0.099 89.735 68 −1393 0.10484.977 132 −916 0.717 59.437 7 5 −1863 0.100 89.636 69 −1386 0.10984.873 133 −909 0.709 58.720 8 6 −1855 0.094 89.536 70 −1378 0.10784.764 134 −902 0.707 58.011 9 7 −1848 0.090 89.442 71 −1371 0.11284.657 135 −894 0.685 57.303 10 8 −1840 0.095 89.352 72 −1364 0.11384.545 136 −887 0.744 56.618 11 9 −1833 0.087 89.256 73 −1356 0.10484.432 137 −879 0.725 55.874 12 10 −1825 0.089 89.170 74 −1349 0.13484.328 138 −872 0.739 55.149 13 11 −1818 0.076 89.080 75 −1341 0.12084.194 139 −864 0.784 54.410 14 12 −1811 0.084 89.004 76 −1334 0.14584.074 140 −857 0.832 53.625 15 13 −1803 0.086 88.921 77 −1326 0.13483.929 141 −849 0.818 52.794 16 14 −1796 0.087 88.835 78 −1319 0.16783.795 142 −842 0.835 51.975 17 15 −1788 0.082 88.748 79 −1311 0.16883.628 143 −835 0.826 51.140 18 16 −1781 0.083 88.666 80 −1304 0.17483.460 144 −827 0.828 50.314 19 17 −1773 0.072 88.582 81 −1296 0.17783.286 145 −820 0.842 49.486 20 18 −1766 0.078 88.511 82 −1289 0.18283.109 146 −812 0.835 48.643 21 19 −1758 0.073 88.433 83 −1282 0.19082.926 147 −805 0.854 47.808 22 20 −1751 0.075 88.360 84 −1274 0.19282.736 148 −797 0.812 46.954 23 21 −1744 0.069 88.285 85 −1267 0.20982.544 149 −790 0.858 46.142 24 22 −1736 0.071 88.216 86 −1259 0.23082.335 150 −782 0.818 45.285 25 23 −1729 0.067 88.145 87 −1252 0.22182.105 151 −775 0.762 44.467 26 24 −1721 0.069 88.078 88 −1244 0.23381.883 152 −767 0.753 43.705 27 25 −1714 0.061 88.009 89 −1237 0.24481.650 153 −760 0.712 42.951 28 26 −1706 0.070 87.949 90 −1229 0.25681.406 154 −753 0.676 42.239 29 27 −1699 0.068 87.878 91 −1222 0.27581.150 155 −745 0.672 41.563 30 28 −1691 0.067 87.810 92 −1215 0.28880.875 156 −738 0.661 40.891 31 29 −1684 0.066 87.743 93 −1207 0.28780.586 157 −730 0.641 40.230 32 30 −1676 0.069 87.677 94 −1200 0.31180.299 158 −723 0.627 39.589 33 31 −1669 0.069 87.608 95 −1192 0.33679.989 159 −715 0.642 38.962 34 32 −1662 0.062 87.539 96 −1185 0.31579.653 160 −708 0.598 38.320 35 33 −1654 0.061 87.477 97 −1177 0.34079.338 161 −700 0.633 37.723 36 34 −1647 0.060 87.416 98 −1170 0.33478.998 162 −693 0.627 37.090 37 35 −1639 0.065 87.356 99 −1162 0.36578.664 163 −685 0.620 36.463 38 36 −1632 0.066 87.291 100 −1155 0.36078.298 164 −678 0.649 35.843 39 37 −1624 0.056 87.225 101 −1147 0.38377.939 165 −671 0.661 35.194 40 38 −1617 0.063 87.168 102 −1140 0.39877.555 166 −663 0.648 34.533 41 39 −1609 0.061 87.106 103 −1133 0.40577.158 167 −656 0.695 33.886 42 40 −1602 0.067 87.045 104 −1125 0.42576.753 168 −648 0.669 33.190 43 41 −1595 0.061 86.978 105 −1118 0.44276.327 169 −641 0.653 32.522 44 42 −1587 0.063 86.917 106 −1110 0.45075.885 170 −633 0.657 31.868 45 43 −1580 0.065 86.854 107 −1103 0.47575.434 171 −626 0.643 31.211 46 44 −1572 0.062 86.790 108 −1095 0.50074.960 172 −618 0.585 30.568 47 45 −1565 0.063 86.728 109 −1088 0.52874.460 173 −611 0.566 29.984 48 46 −1557 0.068 86.665 110 −1080 0.53573.932 174 −604 0.561 29.417 49 47 −1550 0.061 86.596 111 −1073 0.54573.397 175 −596 0.517 28.856 50 48 −1542 0.069 86.535 112 −1065 0.59272.852 176 −589 0.512 28.339 51 49 −1535 0.061 86.466 113 −1058 0.60572.260 177 −581 0.466 27.827 52 50 −1527 0.072 86.405 114 −1051 0.62671.655 178 −574 0.448 27.361 53 51 −1520 0.074 86.333 115 −1043 0.63471.029 179 −566 0.442 26.913 54 52 −1513 0.068 86.259 116 −1036 0.67470.395 180 −559 0.423 26.471 55 53 −1505 0.069 86.191 117 −1028 0.66169.722 181 −551 0.413 26.048 56 54 −1498 0.066 86.122 118 −1021 0.69969.060 182 −544 0.420 25.636 57 55 −1490 0.066 86.056 119 −1013 0.69168.362 183 −536 0.392 25.216 58 56 −1483 0.080 85.990 120 −1006 0.71567.671 184 −529 0.367 24.824 59 57 −1475 0.077 85.910 121 −998 0.71066.956 185 −522 0.387 24.457 60 58 −1468 0.078 85.833 122 −991 0.71466.245 186 −514 0.355 24.070 61 59 −1460 0.078 85.755 123 −984 0.68465.531 187 −507 0.340 23.715 62 60 −1453 0.076 85.677 124 −976 0.69664.847 188 −499 0.352 23.375 63 61 −1445 0.073 85.601 125 −969 0.69564.151 189 −492 0.365 23.023 64 62 −1438 0.089 85.529 126 −961 0.66063.456 190 −484 0.380 22.658 65 63 −1431 0.089 85.440 127 −954 0.66362.796 191 −477 0.383 22.278 P Q R S Bright- Rel. Area ness Height AreaBearing 1 level [μm] % [%] % [%] 2 192 −469 0.386 21.895 3 193 −4620.424 21.509 4 194 −455 0.429 21.085 5 195 −447 0.448 20.675 6 196 −4400.462 20.208 7 197 −432 0.484 19.746 8 198 −425 0.512 19.262 9 199 −4170.574 18.751 10 200 −410 0.600 18.177 11 201 −402 0.631 17.577 12 202−395 0.670 16.946 13 203 −387 0.702 16.275 14 204 −380 0.741 15.574 15205 −373 0.713 14.832 16 206 −365 0.720 14.120 17 207 −358 0.682 13.40018 208 −350 0.680 12.718 19 209 −343 0.634 12.038 20 210 −335 0.61211.404 21 211 −328 0.587 10.792 22 212 −320 0.560 10.205 23 213 −3130.533 9.645 24 214 −305 0.484 9.112 25 215 −298 0.458 8.628 26 216 −2910.446 8.170 27 217 −283 0.408 7.724 28 218 −276 0.394 7.316 29 219 −2680.364 6.922 30 220 −261 0.358 6.558 31 221 −253 0.318 6.200 32 222 −2460.300 5.883 33 223 −238 0.280 5.583 34 224 −231 0.295 5.303 35 225 −2240.285 5.008 36 226 −216 0.286 4.723 37 227 −209 0.272 4.437 38 228 −2010.304 4.165 39 229 −194 0.293 3.861 40 230 −186 0.315 3.569 41 231 −1790.295 3.254 42 232 −171 0.274 2.959 43 233 −164 0.289 2.685 44 234 −1560.259 2.395 45 235 −149 0.242 2.136 46 236 −142 0.238 1.895 47 237 −1340.190 1.657 48 238 −127 0.196 1.467 49 239 −119 0.171 1.271 50 240 −1120.158 1.100 51 241 −104 0.153 0.942 52 242 −97 0.138 0.789 53 243 −890.117 0.651 54 244 −82 0.120 0.535 55 245 −75 0.104 0.414 56 246 −670.091 0.311 57 247 −60 0.066 0.220 58 248 −52 0.054 0.154 59 249 −450.043 0.100 60 250 −37 0.022 0.057 61 251 −30 0.021 0.035 62 252 −220.007 0.014 63 253 −15 0.003 0.006 64 254 −7 0.002 0.003 65 255 0 0.0010.001

[0095] A B C D E F G H I J K L M N O P Q R S Rel. Rel. Rel. Bri- Rel.Area Bri- Area Area Bri- Area Area Bri- Area Area ness Hei- Area Bear-ness Height per. Bearing ness Height Per. Bearing ness ght Per. Bearingle- ght Per. ing % 1 level [μm] [%] [%] level [μm] [%] [%] level [μm][%] [%] vel [μm] [%] [%] 35 33 −1654 0.061 u87.477 97 −1177 0.340 79.338161 −700 0.633 37.723 225 −224 0.285 5.008 36 34 −1647 0.060 87.416 98−1170 0.334 78.998 162 −693 0.627 37.090 226 −216 0.286 4.723 37 35−1639 0.065 87.356 99 −1162 0.365 78.664 163 −685 0.620 36.463 227 −2090.272 4.437 38 36 −1632 0.066 87.291 100 −1155 0.360 78.298 164 −6780.649 35.843 228 −201 0.304 4.165 39 37 −1624 0.056 87.225 101 −11470.383 77.939 165 −671 0.661 35.194 229 −194 0.293 3.861 40 38 −16170.063 87.168 102 −1140 0.398 77.555 166 −663 0.648 34.533 230 −186 0.3153.569 41 39 −1609 0.061 87.106 103 −1133 0.405 77.158 167 −656 0.69533.886 231 −179 0.295 3.254 42 40 −1602 0.067 87.045 104 −1125 0.42576.753 168 −648 0.669 33.190 232 −171 0.274 2.959 43 41 −1595 0.06186.978 105 −1118 0.442 76.327 169 −641 0.653 32.522 233 −164 0.289 2.68544 42 −1587 0.063 86.917 106 −1110 0.450 75.885 170 −633 0.657 31.868234 −156 0.259 2.395 45 43 −1580 0.065 86.854 107 −1103 0.475 75.434 171−626 0.643 31.211 235 −149 0.242 2.136 46 44 −1572 0.062 86.790 108−1095 0.500 74.960 172 −618 0.585 30.568 236 −142 0.238 1.895 47 45−1565 0.063 86.728 109 −1088 0.528 74.460 173 −611 0.566 29.984 237 −1340.190 1.657 48 46 −1557 0.068 86.665 110 −1080 0.535 73.932 174 −6040.561 29.417 238 −127 0.196 1.467 49 47 −1550 0.061 86.596 111 −10730.545 73.397 175 −596 0.517 28.856 239 −119 0.171 1.271 50 48 −15420.069 86.535 112 −1065 0.592 72.852 176 −589 0.512 28.339 240 −112 0.1581.100 51 49 −1535 0.061 86.466 113 −1058 0.605 72.260 177 −581 0.46627.827 241 −104 0.153 0.942 52 50 −1527 0.072 86.405 114 −1051 0.62671.655 178 −574 0.448 27.361 242 −97 0.138 0.789 53 51 −1520 0.07486.333 115 −1043 0.634 71.029 179 −566 0.442 26.913 243 −89 0.117 0.65154 52 −1513 0.068 86.259 116 −1036 0.674 70.395 180 −559 0.423 26.471244 −82 0.120 0.535 55 53 −1505 0.069 86.191 117 −1028 0.661 69.722 181−551 0.413 26.048 245 −75 0.104 0.414 56 54 −1498 0.066 86.122 118 −10210.699 69.060 182 −544 0.420 25.636 246 −67 0.091 0.311 57 55 −1490 0.06686.056 119 −1013 0.691 68.362 183 −536 0.392 25.216 247 −60 0.066 0.22058 56 −1483 0.080 85.990 120 −1006 0.715 67.671 184 −529 0.367 24.824248 −52 0.054 0.154 59 57 −1475 0.077 85.910 121 −998 0.710 66.956 185−522 0.387 24.457 249 −45 0.043 0.100 60 58 −1468 0.078 85.833 122 −9910.714 66.245 186 −514 0.355 24.070 250 −37 0.022 0.057 61 59 −1460 0.07885.755 123 −984 0.684 65.531 187 −507 0.340 23.715 251 −30 0.021 0.03562 60 −1453 0.076 85.677 124 −976 0.696 64.847 188 −499 0.352 23.375 252−22 0.007 0.014 63 61 −1445 0.073 85.601 125 −969 0.695 64.151 189 −4920.365 23.023 253 −15 0.003 0.006 64 62 −1438 0.089 85.529 126 −961 0.66063.456 190 −484 0.380 22.658 254 −7 0.002 0.003 65 63 −1431 0.089 85.440127 −954 0.663 62.796 191 −477 0.383 22.278 255 0 0.001 0.001

[0096] “Bearing-area-percentage” in the sense of the method ofevaluation in accordance with the invention is defined as the surface tobe measured which would contact planarly with an imaginary contactsurface area having a geometrically ideal planar surface without theeffect of a squeezing force when the warp and weft wires of the fabriccloth in coming from above from the highest point of contact areprogressively reduced in thickness quasi continuously, with it having tobe noted In this arrangement that due to grinding, the actual surfacearea, i.e. also the reduction in the warp or weft wire areas, is takeninto account whilst a laser sensor below the largest contact surfacearea only “sees” their projection. For example, this theoreticalconsideration may be undertaken within the two limits 30% and 60%bearing-area-percentage.

[0097] As regards defining the projected section area the following isto be noted. In height measuring using e.g. a laser sensor it must betaken into account that the sectional area measured is not the truesectional area but the projected sectional area. This is a projectedsectional area because measuring is done at right angles to the surfaceof the object measured from above downwards and the laser is unable to“see” contours concealed by overlaps e.g. such as those below thelargest extent of a wire. This is why the “sectional area”, e.g. of awire, no longer becomes smaller when height ranges are measured locatedbelow the largest extent of the wire forming the contour. This opticallynecessitated section area is the projected section area.

[0098] The following further definitions are given for the relativepocket depth, measuring height “0” and bearing-area-percentage. Therelative pocket depth is the quotient of the difference in heightbetween the measuring height at which the bearing-area-percentage is 30%and the measuring height at which the bearing-area-percentage is 60% andthe sum of the diameters of a weft wire and a warp wire. Measuringheight “0” is the outer limit of the paper-making-machine fabric on thepaper contact side. The bearing-area-percentage is the projected area ofthe sectional wires of the fabric at a specific measuring height dividedby the measuring area, wherein the sectional planes are located parallelto the surface of the fabric.

[0099] When comparing conventionally woven and subsequentlyconventionally heat set, single-ply TAD fabrics to embodiments inaccordance with the invention, it is obvious that conventional fabricsof this kind are clearly below a critical value whereas embodiments ofthe TAD fabrics in accordance with the invention are above this criticalvalue.

[0100] The “characteristic critical value” of embodiments in accordancewith the invention of single-ply TAD fabrics is defined as the “relativepocket depth” permitting an indication of the suitability of a TADpocket in accordance with the invention irrespective of the selectedwarp and weft wire diameter of the fabric selected in each case.Relativizing the system in this way is done by relating the differencein height between the height for a bearing-area-percentage of 30% andthe height for a bearing-area-percentage of 60% to the sum of the weftand warp wire diameters.

[0101] The “characteristic critical value” for selecting embodiments inaccordance with the invention is a “relative pocket depth” of >/=20%,preferably >/=24% and most preferably >/=27%. Conventional TAD fabricspecimen exhibit a “relative pocket depth” significantly below 20%.

[0102] Stipulating a “relative pocket depth” is good practice since theoptimising method is intended to furnish a selection in comparing TADfabric structures of equal weft and warp wire diameter, the addedthickness for an increase in the weft and warp wire diameter beingnegligible by contrast.

1. A paper-making-machine fabric, in the form of a woven pattern, suchas a through air drying (TAD) fabric, wherein the relative pocket depthof pockets in the paper-making-machine fabric open towards the papercontact side amounts to 20% or more, where the relative pocket depth isthe quotient of the difference in height between the measuring height atwhich the bearing-area-percentage is 30% and the measuring height atwhich the bearing-area-percentage is 60% and the sum of the diameters ofa weft wire and a warp wire, the measuring height “0” is the outer limitof the paper-making-machine fabric on the paper contact side, thebearing-area-percentage is the projected area of the sectional wires ofthe fabric at a specific measuring height divided by the measuring areawherein the sectional planes are located parallel to the surface of thefabric.
 2. The paper-making-machine fabric as set forth in claim 1,characterized in that the relative pocket depth amounts to 24% or more.3. The paper-making-machine fabric as set forth in claim 1,characterized in that the relative pocket depth amounts to 27% or more.4. The paper-making-machine fabric as set forth in claim 1,characterized in that the fabric comprises a woven pattern regularlyrepeated over the surface area.
 5. The paper-making-machine fabric asset forth in claim 1, characterized in that the fabric comprises a wovenpattern irregularly distributed over the surface area.
 6. Thepaper-making-machine fabric as set forth in claim 1, characterized inthat the fabric is single-ply.
 7. A tissue-paper product produced with apaper-making-machine fabric as set forth in any of the claims 1 to 6.